hardMultiple Choice
300-410 OSPF virtual link Practice Question
An engineer configures OSPFv2 with a virtual link to connect a non-backbone area to area 0. The virtual link is not coming up, and routes from the non-backbone area are not being advertised into area 0. Which is the most likely explanation?
⚠ Common exam trap
Candidates often overlook that virtual links cannot traverse stub areas. This question tests that rule.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The transit area is a stub area.
In OSPF, virtual links cannot be configured through stub areas. If the transit area is a stub area, the virtual link will not function correctly, and routes from the non-backbone area will not be advertised into area 0. Even if the virtual link appears to be up (e.g., due to misconfiguration or software bug), route propagation is blocked because stub areas do not allow virtual links or type 5 LSAs. Therefore, the most likely explanation is that the transit area is a stub area.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The virtual link is configured only on one router.
Why it's wrong here
If the virtual link is configured on only one router, the adjacency cannot form. Since the stem states the virtual link is up, this cannot be the cause.
- ✓
The transit area is a stub area.
Why this is correct
Correct. A virtual link through a stub area is invalid in OSPF. The transit area must be a standard area or an NSSA, not a stub area.
- ✗
The OSPF process is configured with 'no-virtual-link' command.
Why it's wrong here
The 'no-virtual-link' command is not a standard OSPF command; it is likely a distractor. If the virtual link is up, this command has not been applied.
- ✗
The router IDs are not reachable via the transit area.
Why it's wrong here
If router IDs were not reachable via the transit area, the virtual link would not establish. Since the virtual link is up, reachability is confirmed.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 300-410 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 300-410 exam.